1. Field of the Invention
The invention relates to a storage subsystem on which plural different types of storage devices such as a hard disc drive and a flash memory as storage resources are mounted. The invention further relates to a storage system including a storage subsystem, an upper system and a storage device.
2. Description of the Related Art
The storage subsystem is known as a control system for storing data of the upper system such as a host in storage devices.
The storage subsystem includes a first interface control unit controlling data transmission and reception with respect to the upper system, a second interface control unit controlling data transmission and reception with respect to plural storage devices and a controller controlling data traffic between the host and storage devices.
A hard disk drive (HDD) has been used as the storage device in related arts, however, semiconductor memories such as a flash memory are coming into use as a storage resource for the storage subsystem because a manufacturing unit price of the flash memory is reduced. There exists a storage system on which both the HDD and a flash memory drive (SSD) are mounted as storage devices. There is a related art disclosed in JP-A-2008-134776 as the one concerning the present invention.    Patent Document: JP-A-2008-134776